Neutrons!

Current images of fusor efforts, components, etc. Try to continuously update from your name, a current photo using edit function. Title post with your name once only. Change image and text as needed. See first posting for details.
User avatar
Richard Hull
Moderator
Posts: 14992
Joined: Fri Jun 15, 2001 9:44 am
Real name: Richard Hull

Re: Neutrons!

Post by Richard Hull »

Nice thoughts and ideas. Another way to try and skin th' cat. If your system continues to work better as it is develops, you might just put the old fusor stock construction out of biz and every one with the goods and istrumentation might move over to 2.75 or 4 inch crosses!! I mean it!

I wonder how much the sharper radius joints at the cross arms add to the emission/ionization patterns. I realize the welds are smoothed but still sharper radius than the wall by huge amounts. Just thinking out loud.

We will see how far you can push this puppy.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
User avatar
Garrett Young
Posts: 123
Joined: Fri May 26, 2006 9:51 pm
Real name: Garrett Young

Re: Neutrons!

Post by Garrett Young »

Richard,

On the onset of this project I performed simulations using FEMM (free here - http://www.femm.info/wiki/HomePage) and custom code in Mathematica to try and optimize the electric field gradient (ion optics approach) and achieve a potential well at the center of the device nearly equal to the applied potential. Many wire grid designs don't effectively "shield" the grounded shell and only have the applied potential near the grid wires (5-10kV less in the center). My electrode design achieves 97% of the applied potential in the center and its shape (along with the contoured end cap inserts) focuses the ions through the center.

At the cross
KF50-40-port.png
Elsewhere
KF50-40-noport.png
(Note: The actual fusor volume is only 8.8 cubic inches.)
- Garrett
User avatar
Garrett Young
Posts: 123
Joined: Fri May 26, 2006 9:51 pm
Real name: Garrett Young

Re: Neutrons!

Post by Garrett Young »

- Garrett
User avatar
Garrett Young
Posts: 123
Joined: Fri May 26, 2006 9:51 pm
Real name: Garrett Young

Re: Neutrons!

Post by Garrett Young »

31 Bubbles in 4 minutes (24 bub/mrem dosimeter), 12.5cm distance to cathode, TIER 296K n/sec
IMG_1540.png
- Garrett
User avatar
Garrett Young
Posts: 123
Joined: Fri May 26, 2006 9:51 pm
Real name: Garrett Young

Re: Neutrons!

Post by Garrett Young »

Multiple runs over 300k n/s (344k n/s max)
Activating Indium at ~2x background and Silver ~3.5x background

Code: Select all

Run                      Avg. Background              1 min. Indium Count
In_1800_03162017         36.6                         72
In_1816_03162017         34.3                         80
In_1825_03162017         33.5                         62
In_1833_03162017         33.0                         57

Run                      Avg. Background              1 min. Silver Count
Ag_2252_03172017         40.3                         138
Basically, I never turn the vacuum pump off now and force convection cool the pump to achieve lower base pressure and cleaner system. In addition, I've optimized the deuterium flow rate and pump valve conductance for optimal pressure profile during the run.
- Garrett
User avatar
Garrett Young
Posts: 123
Joined: Fri May 26, 2006 9:51 pm
Real name: Garrett Young

Re: Neutrons!

Post by Garrett Young »

Added axial magnetic field last night using ceramic magnets at opposing ends. Fairly uniform 200 gauss in the cathode region and 300 gauss at the shaped anodes (which probably improves ionization at the wall, thus increasing average ion energy). Pressure is still 48-58 mTorr during runs. Base pressure has lowered to 3 mTorr (I'm using just a 2-stage rotary pump).
axial-mag.png
Runs are now above 400k n/sec (420k n/sec best run - corroborated with bubble dosimeter). It seems the level of fusion per input power per chamber volume is very high (8.39E+04, n/sec/kW/in^3).

I have my hybrid NIM/Sound Card gamma spectrometer up and running and I'm interested in activating Manganese next.
- Garrett
User avatar
Garrett Young
Posts: 123
Joined: Fri May 26, 2006 9:51 pm
Real name: Garrett Young

Re: Neutrons!

Post by Garrett Young »

I can't stress enough the importance of conditioning runs with deuterium to ultimately achieve maximum neutron production rates. I know this topic has been addressed, but it's worth another mention. I consistently see a ~3x gain between first few plasmas after the system was brought to atmosphere and the last runs.

Wall loading, system purity, etc. all seem to be contributing factors.

My latest numbers with the mini-linear-fusor configuration (Max Cathode Voltage 28.6kV):
3 mins: 431k n/s, Q 9.84E-10
4 mins: 357k n/s
5 mins: 263k n/s
- Garrett
User avatar
Dennis P Brown
Posts: 3160
Joined: Sun May 20, 2012 10:46 am
Real name: Dennis Brown

Re: Neutrons!

Post by Dennis P Brown »

Really good scientific work you are performing. You make me realize I should not have abandoned my original fusor that was to based on a 2.75 inch cross. Instead, I decided to use my large surplus chamber and while successful, achieved barely a tenth of the neutron flux you have. I agree with Richard that this approach demonstrates that this design has a lot of advantages; guess it will likely become the "gold" standard for fusor design in the fusor.
User avatar
Richard Hull
Moderator
Posts: 14992
Joined: Fri Jun 15, 2001 9:44 am
Real name: Richard Hull

Re: Neutrons!

Post by Richard Hull »

Garrett, thanks for blowing on the same trumpet I have been tooting on for many years here. It is all about "conditioning the fusor" and the "ability to operate the fusor properly by a skilled hand". The former is seen only after the latter is obtained via the "doing". Fusion in the fusor moves onward and upward through operation and the use and understanding of full and proper instrumentation. The instrumentation need not be calibrated to a high order, but must be capable of showing a run-to-run improvement in performance.

Once the above is attained, calibration can proceed to get a more precise figure on what one is doing and has accomplished. It is a great pity that the rather accurate and final arbiter, the bubble dosimeter, is both rather expensive and sports a limited useful lifetime. I bought them twice. Once in ignorance to prove fusion and get numbers and then 2 years later to calibrate, forever, my 3He detector setup which to this day performs to relative accuracy based on the large amount of data taken during the last lifespan of that second bubble dosimeter. I derived a calibration factor from this data which is now applied to an electronic, timed count in order to obtain my isotropic emission figures.

Keep up the good work and tooting that horn as in your above post. It is a revelation that few will ever see as so many are greedy only for the "win" and never operate their fusor in the manner and never packed the gear to continue on to the realization of what we have seen. I would think that only about 20% on the neutron club list have seen and done what we have done to its full and final realization.

Once you squeeze that last bit of fusion out of your system.....and it will come.....You are in full command of the IEC fusion concept and realize only a redesign or more powerful supply can take the system to greater heights of performance.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
Dan Knapp
Posts: 402
Joined: Wed Aug 06, 2008 8:34 am
Real name: Dan Knapp

Re: Neutrons!

Post by Dan Knapp »

Garrett, You would be interested in seeing the information on Alex Klein's "MARBLE" reactor (google Alex Klein and MARBLE). He built this device in the dying days of his company and then rode off into the sunset in Malaysia. It is essentially multiple's of your device superimposed to overcome the limitations of space charge at the turning points. It also included an axial magnetic field. He filed a patent on it (application was published) but I've not seen that the patent has ever actually issued. There might be some information from his work that would be helpful to you.
User avatar
Garrett Young
Posts: 123
Joined: Fri May 26, 2006 9:51 pm
Real name: Garrett Young

Re: Neutrons!

Post by Garrett Young »

Interesting. Thank you for sharing. I'll have to read more about their device.

Part of choosing the dimensions for my device was making sure child-langmuir space charge didn't limit the ion beam current.
- Garrett
User avatar
Garrett Young
Posts: 123
Joined: Fri May 26, 2006 9:51 pm
Real name: Garrett Young

Re: Neutrons!

Post by Garrett Young »

Attempted a gamma spec of Indium (background removed). The signal to noise isn't great but that's probably due to the short activation time and low neutron numbers. In addition, it seems the detector is more sensitive to lower energy gammas. Does that make sense for a NaI crystal? Can Theremino MCA be calibrated for this variation in sensitivity using the energy equalizer?
ThereminoMCA_20170403_In.png
- Garrett
User avatar
Richard Hull
Moderator
Posts: 14992
Joined: Fri Jun 15, 2001 9:44 am
Real name: Richard Hull

Re: Neutrons!

Post by Richard Hull »

The lower end of NaI:Tl xtals are always a noise fest, as the background is a mix of low energy gammas, xrays and weakened cosmic interactions with local matter. The only thing you can background out are terrestrial NORM signals as they are present and rather constant. Random cosmic interactions are not so easy. Depending on the crystal size, low energy stuff, (noise in low energy end), is 100% captured in the xtal and makes a flash. Lots of clutter under 50kev and only a strong source will push out of it enough to be seen easily. Log mode energy display will often assist, but you will never have sharp peaks from and NaI:Tl crystal.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
User avatar
Garrett Young
Posts: 123
Joined: Fri May 26, 2006 9:51 pm
Real name: Garrett Young

Re: Neutrons!

Post by Garrett Young »

Acquired a new power supply capable of -60kV and 11mA and have performed several lower power runs and the results are very exciting.

Pressure: 33 mTorr
Cathode Voltage: 44.1 kV
Cathode Current: 10.9 mA

TIER: 1.30 E+6 n/sec (!!)
Q: 3.16 E-9
- Garrett
User avatar
Steven Sesselmann
Posts: 2127
Joined: Wed Aug 10, 2005 9:50 pm
Real name: Steven Sesselmann
Location: Sydney - Australia
Contact:

Re: Neutrons!

Post by Steven Sesselmann »

Garrett,

Congratulations on reaching the mega neutron mark, well done.

My next target..

Steven
http://www.gammaspectacular.com - Gamma Spectrometry Systems
https://www.researchgate.net/profile/Steven_Sesselmann - Various papers and patents on RG
User avatar
Garrett Young
Posts: 123
Joined: Fri May 26, 2006 9:51 pm
Real name: Garrett Young

Re: Neutrons!

Post by Garrett Young »

Thanks Steven.

I ran tonight with my rebuilt Spellman DXM70N600 (viewtopic.php?f=11&t=11146&start=146) and sustained >1 E+6 n/sec for a couple of minutes.

Though this performance may be standard for the stock 6 inch fusor, it seems this is several multiples above previous results from a compact fusor.
- Garrett
Andrew Seltzman
Posts: 815
Joined: Sun Feb 01, 2004 8:02 pm
Real name: Andrew Seltzman
Contact:

Re: Neutrons!

Post by Andrew Seltzman »

I agree, there hasn't been(on this forum) a compact system with this output level. The compact system would allow a sample to be placed closer to the center allowing faster neutron activation.

I noticed you have a patent pending sticker on your custom inverter, was this built just for the spellman supply?
Andrew Seltzman
www.rtftechnologies.org
User avatar
Garrett Young
Posts: 123
Joined: Fri May 26, 2006 9:51 pm
Real name: Garrett Young

Re: Neutrons!

Post by Garrett Young »

The custom inverter was designed/built especially for the Spellman DXM70N600 (and can be modified for other DXM models).

The "patent pending" label came printed on the extruded heatsink I'm using for the IGBTs. I'm not seeking a patent for the design, but if you wanted the operational ease of a x-ray transformer with the compactness/weight of a smps this is the way to do it. I have been thinking about designing a power supply especially for fusors. Targeting low cost and about 300W (40kV/7.5mA). The user would supply the variac and panel meters and I would provide the inverter and high voltage section.
- Garrett
RobertTubbs
Posts: 209
Joined: Thu Mar 05, 2009 1:49 pm
Real name:

Re: Neutrons!

Post by RobertTubbs »

Really cool project Garrett, and nice work. This concept has been on my list of things to try as it functions much like a beam on target system would but with discharge mantained and directed by the central cathode. I ultimately opted for the persuit of monoatomic species of ions for their favorable qualities during bombardment. Your config here is an excellent, though not commonly discussed route to what basically amounts to a twin diatomic beamed beam-target arrangement. Your conditioning is the loading of deuterium into the materials on the two ends of the beams' axis. Though most documentation will say to use Ti for loading, you can use a Ti cathode and it'll sputter your vessel with an appropriate thickness of Ti during a bit of operation, just leave it in if you do this. Alternatively you can just use solid aluminum ends which perform twice as well as a thick (non-sputter layer thickness) piece of Ti. Either of these should increase your yields by a factor of some number.

This thread's ultra-premium quality is like something out of the early days of the forum.
RT
User avatar
Garrett Young
Posts: 123
Joined: Fri May 26, 2006 9:51 pm
Real name: Garrett Young

Re: Neutrons!

Post by Garrett Young »

New personal best:

Cathode Voltage: 59.8 kV
Cathode Current: 8.5 mA
Pressure: 28 mTorr

TIER: 1.74 E+6
Q: 4.01 E-9
- Garrett
User avatar
Garrett Young
Posts: 123
Joined: Fri May 26, 2006 9:51 pm
Real name: Garrett Young

Re: Neutrons!

Post by Garrett Young »

I modified my 60kV/11mA power supply to deliver a maximum of 26mA using the same driver design I engineered to fix the broken DXM70N600 supply.

Cathode Voltage: 53kV
Cathode Current: 16 mA
Pressure: 24 mTorr
Duration: 100 seconds
TIER: 2,021,688 (!!)
- Garrett
User avatar
Richard Hull
Moderator
Posts: 14992
Joined: Fri Jun 15, 2001 9:44 am
Real name: Richard Hull

Re: Neutrons!

Post by Richard Hull »

Fabulous! I hope you are measuring and shielding your x-rays that are obviously coming out of the device with a vengeance!
You are into a serious voltage and current level now where x-rays are a significant hazard.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
User avatar
Garrett Young
Posts: 123
Joined: Fri May 26, 2006 9:51 pm
Real name: Garrett Young

Re: Neutrons!

Post by Garrett Young »

Absolutely. Before raising the voltage to 40kV and beyond, I installed a lead shield (1/16 inch) and now operate the device at a greater distance. I have a 200 mRem dosimeter and survey meter that I use to monitor x-rays.


Side Note: In my last post, I didn't include units for the TIER number. It is indeed neutrons per second.
- Garrett
User avatar
Garrett Young
Posts: 123
Joined: Fri May 26, 2006 9:51 pm
Real name: Garrett Young

Re: Neutrons!

Post by Garrett Young »

NEW Personal Best!

Cathode Voltage: 52kV
Cathode Current: 12 mA
Pressure: 30 mTorr
Duration: 25 seconds
TIER (n/sec): 2,703,420 - electronic detection, 2,750,000 - dosimeter
Record-25June2017.png
Note: The RMS voltage and current isn't being calculated correctly (artificially low)
- Garrett
User avatar
Richard Hull
Moderator
Posts: 14992
Joined: Fri Jun 15, 2001 9:44 am
Real name: Richard Hull

Re: Neutrons!

Post by Richard Hull »

That is fabulous! A record for so small a chamber.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
Post Reply

Return to “Images du Jour”